1. Field of the Invention
This invention relates to a flat panel display device, and more particularly to a plasma display panel that is capable of improving the discharge and light-emission efficiencies and the brightness.
2. Description of the Related Art
Generally, a plasma display panel (PDP) radiates a fluorescent body by an ultraviolet with a wavelength of 147 nm generated during a discharge of He+Xe or Ne+Xe gas to thereby display a picture including characters and graphics. Such a PDP is easy to be made into a thin film and large-dimension type. Moreover, the PDP provides a very improved picture quality owing to a recent technical development. The PDP is largely classified into a direct current (DC) driving system and an alternating current (AC) driving system. The DC-type PDP causes an opposite discharge between an anode and a cathode provided at a front substrate and a rear substrate, respectively to display a picture. On the other hand, the AC-type PDP allows an alternating voltage signal to be applied between electrodes having dielectric layer therebetween to generate a discharge every half-period of the signal, thereby displaying a picture. Since such an AC-type PDP uses a dielectric material which allows a wall charge to be accumulated on the surface thereof upon discharge, it produces a memory effect.
Referring to FIG. 1, the AC-type PDP includes a front substrate 10 provided with a sustaining electrode 12, and a rear substrate 20 provided with an address electrode 22. The front substrate 10 and the rear substrate 20 are spaced in parallel to each other with having a barrier rib 26 therebetween. A mixture gas, such as Nexe2x80x94Xe or Hexe2x80x94Xe, etc., is injected into a discharge space defined by the front substrate 10, the rear substrate 20 and a barrier rib 26. The sustaining electrode 12 makes a pair by two within a single of plasma discharge channel. Any one of the pair of sustaining electrode 12 is used as a scanning/sustaining electrode that responds to a scanning pulse applied in an address interval to cause an opposite discharge along with the address electrode 22 while responding to a sustaining pulse applied in a sustaining interval to cause a surface discharge with the adjacent sustaining electrodes 12. Also, the remaining one of the sustaining electrode pair 12 is used as a common sustaining electrode to which a sustaining pulse is applied commonly. On the front substrate 10 provided with the sustaining electrode pair 12, a dielectric layer 24 and a protective layer 18 are disposed. The dielectric layer 24 is responsible for limiting a plasma discharge current as well as accumulating a wall charge during the discharge. The protective film 18 prevents a damage of the dielectric layer 24 caused by the sputtering generated during the plasma discharge and improves the emission efficiency of secondary electrons. This protective film 18 is usually made from MgO. Barrier ribs 26 for dividing the discharge space is extended perpendicularly at the rear substrate 2. On the surfaces of the rear substrate 20 and the barrier ribs 26, a fluorescent material 28 excited by a vacuum ultraviolet lay to generate a visible light is provided.
In such an AC-type PDP, one frame consists of a number of sub-fields so as to realize gray levels by a combination of the sub-fields. For instance, when it is intended to realize 256 gray levels, one frame interval is time-divided into 8 sub-fields. Further, each of the 8 sub-fields is again divided into a reset interval, an address interval and a sustaining interval. The entire field is initialized in the reset interval. The discharge pixel cells on which a data is to be displayed are selected by the address discharge in the address interval. The selected cells sustain the discharge in the sustaining interval. The sustaining interval is lengthened by an interval corresponding to 2n depending on a weighting value of each sub-field. In other words, the sustaining interval involved in each of first to eighth sub-fields increases at a ratio of 20, 21, 23, 24, 25, 26 and 27. To this end, the number of sustaining pulses generated in the sustaining interval also increases into 20, 21, 23, 24, 25, 26 and 27 depending on the sub-fields. The brightness and the chrominance of a displayed image are determined in accordance with a combination of the sub-fields.
As shown in FIG. 2, in the conventional PDP, the sustaining discharge begins at a portion between the sustaining electrode pair 12 to make a surface discharge at the surface of the sustaining electrode pair 12. Accordingly, the conventional PDP has a problem in that a light-emission area is extremely limited to have low brightness and efficiency. The brightness of such a PDP is proportional to a quantity of a vacuum ultraviolet ray generated during the discharge. In order to increase a generated quantity of a vacuum ultraviolet ray, there has been suggested a method of lengthening a distance between the sustaining electrode pair 12 to prolong a discharge path or a method of widening an electrode width of the sustaining electrode pair 12 to enlarge a discharge intensity. However, when a distance between the sustaining electrode pair 12 is large, a discharge length is prolonged to increase a generated quantity of a ultraviolet ray, but a discharge initiation voltage rises suddenly at more than a certain distance to cause a difficulty in a real application. When a width of the discharge-sustaining electrode is large, a generated quantity of an ultraviolet ray is increased in accordance with an increase of the discharge intensity. But, because a discharge current is increased in proportion to an electrode width, a wasted amount of the discharge current is increased to cause a disadvantage in respect of the efficiency.
Accordingly, it is an object of the present invention to provide a plasma display panel that is capable of improving the discharge and light-emission efficiency as well as the brightness.
In order to achieve these and other objects of the invention, a plasma display panel according to an embodiment of the present invention includes a sustaining electrode pair formed on an upper substrate in such a manner to be positioned at the edges of a discharge cell; a trigger electrode pair, being positioned between the sustaining electrode pair, to cause a trigger discharge for deriving a sustaining discharge; and dielectric layers formed on the sustaining electrode pair and the trigger electrode pair to have a different thickness.
A plasma display panel according to another embodiment of the present invention includes a sustaining electrode pair formed at a first distance on an upper substrate in such a manner to be positioned at the edges of a discharge cell; a first dielectric layer formed to entirely cover the sustaining electrode pair; a trigger electrode pair formed at a second distance larger than the first distance on the first dielectric layer; and a second dielectric layer formed to entirely cover the first dielectric layer and the trigger electrode pair.
A plasma display panel according to still another embodiment of the present invention includes a trigger electrode pair formed at a first distance on an upper substrate in such a manner to be positioned at the edges of a discharge cell; a first dielectric layer formed to entirely cover the trigger electrode pair; a sustaining electrode pair formed at a second distance larger than the first distance on the first dielectric layer; and a second dielectric layer formed on the first dielectric layer to entirely cover the sustaining electrode pair.
A plasma display panel according to still another embodiment of the present invention includes a sustaining electrode pair formed on an upper substrate in such a manner to be positioned at the edges of a discharge cell; a trigger electrode pair formed on the upper substrate in such a manner to be positioned between the sustaining electrode pair; and dielectric layers formed on the upper substrate to cover the sustaining electrode pair and the trigger electrode pair, said dielectric layers being designed such that the trigger electrode pair has a smaller dielectric constant than the sustaining electrode pair.
A plasma display panel according to still another embodiment of the present invention includes a sustaining electrode pair formed at a first distance on an upper substrate in such a manner to be positioned at the edges of a discharge cell; a first dielectric layer formed to entirely cover the sustaining electrode pair; a trigger electrode pair formed at a second distance larger than the first distance on the first dielectric layer; and a second dielectric layer formed on the first dielectric layer to entirely cover the trigger electrode pair and having a dielectric constant smaller than the first dielectric layer.